First record of molecular and pathological investigations of physalopterid larvae infection in northern palm squirrel Funambulus pennantii.

Around 100 reported species of Physaloptera commonly infect mammals, reptiles, birds, and amphibians. The identification of Physaloptera species solely on morphological characteristics is difficult, especially in the case of larval and congeneric infections. The present study is an attempt to identify molecularly and to perform phylogeny and pathology of natural Physaloptera larval infection in northern palm squirrels. The molecular confirmation of the recovered parasitic stages was performed by targeting the nuclear 18S rRNA gene sequence. Phylogenetic analysis and evolutionary divergence of the present study isolate with GenBank™ archived Physaloptera sequences were performed. The cysts (containing the larval stages) were subjected to histopathological examination. Morphological identification of the larval stages revealed the presence of pseudolabia, two spines, and a collar-like projection at the anterior end. Histopathology of the cysts revealed transverse sections of parasites in the lumen along with the thickened cystic wall, infiltration of mononuclear cells, fibrous tissue proliferation in the wall, and cellular debris in the cystic lumen. The molecularly confirmed and sequenced present study isolate was submitted to GenBank™ under the accession number LC706442. Blast analysis revealed 96.82-98.64% nucleotide homology of the present study isolate to the GenBank™ archived Physaloptera sequences. The isolate of the present study was monophyletic with Physaloptera sp. and P. praeputialis recovered from the cats of Haryana, India. Also, evolutionary divergence studies revealed no difference among these sequences. The present study evinced the most probable role of the northern palm squirrel Funambulus pennantii as an aberrant or second intermediate host for P. praeputialis.